You can make a query report or script report for your needs. Definitely don’t need to store data in DB and no need for a custom page. Refer these links
All you need is an sql query with a union all and select from both doctype tables
Query report
- easy/instant can be done without custom app, directly in UI (stored in DB)
- complex js may be harder, button in row may be more complicated.. refer above links
- just go to your-site/app/report and “Add Report”
Script report
- total control, can do more stuff, esp getting data in py controller
- need custom app, and the baggage that comes with that